Authorities in Australia are investigating a flight in which the pilot fell asleep and overflew the destination by 29 miles.

The charter flight took off from Devonport in Tasmania at 6.21am and was due to land at King Island at 7.46am. 

The pilot of the twin-engined Piper PA-31 aircraft, which can carry about seven people, was the only person on board and appears to have woken up, flown to the destination – a small island off Tasmania – and landed safely. 

The Australian Transport Safety Bureau said it was investigating the flight as a “pilot incapacitation” incident.

“During the cruise, the pilot, who was the only person on board, fell asleep resulting in the aircraft overflying King Island by 46 km [29 miles],” the bureau said.

“As part of the investigation, the ATSB will interview the pilot and review operational procedures.”

It is not clear how the pilot woke up.

Vortex Air, the operator of the flight, said the pilot “unintentionally fell asleep while in command of the aircraft”. It said the flight was the first for the pilot after returning from a period of leave.

“The pilot was the only person on board the aircraft and no one was injured as a result of the incident,” it said.

“The flight was the first scheduled flight for the day… The issue became apparent when Air Traffic Control was unable to contact the pilot in-flight, and the aircraft travelled past the intended destination point while operating on autopilot.”

Vortex Air said the pilot was experienced, had flown the route multiple times and “had declared themselves fit to fly”.

“This is an extremely rare occurrence…  and the company is providing the necessary support to the pilot to assist them to safely return to full duties,” it said.

Neil Hansford, from Strategic Aviation Solutions, said the plane – if the pilot had not woken  – would have flown on autopilot until it ran out of fuel.

"The aircraft will fly until it runs out of fuel, or in some cases the fuel tanks have to be switched over, so once it’s starved of fuel it then crashes," he told ABC News. 

The bureau is expected to release a final report on the incident early next year.